1. Field of the Invention
The present invention generally relates to agricultural seed planting implements and to the depth-setting mechanism on furrow opening assemblies of such implements, and more particularly to an assembly for adjusting the depth-setting mechanism.
2. Description of the Related Art
Farmers utilize a wide variety of seed planting implements, including seed drills and planters. In a known type of planting implement, seed planting or row units are attached to a toolbar extending transverse to the direction of planting. The toolbar is coupled to a tractor or other work vehicle suitable for pulling the planting implement along a field that is to be seeded to a crop. Each planting unit includes a ground penetrating assembly, often including one or more discs, for opening a seed trench or furrow in the ground as the planting implement is pulled across a field. Components of the ground penetrating assembly shape the bottom and sides of the seed trench, and a seed metering device provides individual seeds at a controlled rate for deposit in the seed trench. Furrow closing components of each row unit close the seed trench in a controlled manner.
It is a desirable and perhaps even primary agronomic principle that seeds should be planted at precisely controlled and consistent depths both within a row and from row to row. Since a single planting implement may be used to plant several different types of crops and/or the same crop in different planting locations under different planting and growing conditions, it is necessary that the planting depth is adjustable so that the seeds are placed at a depth that has been determined to be the best for seed germination and plant growth of the particular crop under the existing and anticipated conditions.
To control planting depth, it is known to provide gauge wheels that travel on the surface of the field to control the depth to which the ground penetrating assembly can run, the positions of the gauge wheels being adjustable so that the depth of the seed trench can be controlled within fractions of an inch. Adjustment linkages are provided for changing the relative positioning of the gauge wheels with respect to the ground penetrating assembly. It is known to move the adjustment linkage by a handle connected thereto, the handle engaging a register having multiple positions for securing the handle to maintain the position to which the handle is adjusted.
As growers have gained greater understanding about seed germination and plant growth, and as soil preparation procedures have changed and improved, crop growers have demanded more precise control over seed placement both in the spacing between seeds and in the depth at which the seeds are placed below the soil surface. Accordingly, there is both a demand and a need for even more precise control over the depth of the seed trench that is formed during planting operations. While depth-setting mechanisms have been designed for ever more precise settings, the linkages and other structures forming the depth setting mechanisms have multiple components and connections which can lead to setting errors due to the variable effects of tolerance stack-up, wear and the like. In planting implements having multiple seed planting or row units, it is necessary that all units be similarly calibrated so that all units plant to the same planting depths when set to the same settings. The multiple components and linkages present in depth-setting mechanisms can acquire unacceptably large variations from one row unit to another in the accumulated stack of tolerances in the component parts even when new, and after wear has occurred and/or if parts have been replaced, planting depths can vary significantly between row units that have been adjusted to the same planting depth settings.
What is needed in the art is a structure for zeroing the depth setting mechanisms in a seed planting implement to adjust out the varying effects of tolerance stack-up and wear between different seed planting units of the implement.